vim-patch:9.2.0967: hit-enter prompt eats keys from a running mapping (#41359)

Problem:  The hit-enter prompt fires whenever a message scrolls the screen.
          When this happens while a mapping is being processed, it consumes
          the mapping's next key, causing unexpected behavior for users.
Solution: Similar to what 9.1.1969 did for stuffed characters, skip the
          hit-enter prompt when there are still keys pending from a mapping
          in the typeahead buffer.

related: neovim/neovim#38298
related: neovim/neovim#20635
related: neovim/neovim#30890
closes:  vim/vim#20753

AI assisted.

6025ea9e02

Co-authored-by: XiaowenHu96 <me@xiaowenhu.com>

src/nvim/message.c

@@ -1453,10 +1453,12 @@ void wait_return(int redraw)
     c = CAR;                    // just pretend CR was hit
     quit_more = false;
     got_int = false;
-  } else if (!stuff_empty()) {
-    // When there are stuffed characters, the next stuffed character will
-    // dismiss the hit-enter prompt immediately and have to be put back, so
-    // instead just don't show the hit-enter prompt at all.
+  } else if (!stuff_empty() || !typebuf_typed()) {
+    // When there are stuffed characters or pending mapped characters, the
+    // next character will dismiss the hit-enter prompt immediately.  A
+    // stuffed character then has to be put back, while a mapped character
+    // may even be swallowed (e.g. "g" treated as a message-scrollback key),
+    // so instead just don't show the hit-enter prompt at all.
     c = CAR;
   } else {
     State = MODE_HITRETURN;

test/functional/legacy/messages_spec.lua

@@ -889,6 +889,27 @@ describe('messages', function()
     ]])
   end)
 
+  -- oldtest: Test_hit_enter_no_eat_mapped_keys()
+  it('hit-enter prompt does not eat keys from a mapping', function()
+    screen = Screen.new(75, 10)
+    exec([[
+      set ruler more
+      call setline(1, range(1, 20))
+      " The 8-line :echo scrolls the screen and would raise a hit-enter prompt;
+      " the mapping then runs "gg" to move the cursor to line 1.
+      nnoremap X :echo "a\nb\nc\nd\ne\nf\ng\nh"<CR>gg
+      normal! 10G
+    ]])
+    t.eq({ mode = 'n', blocking = false }, api.nvim_get_mode())
+    t.eq({ 10, 0 }, api.nvim_win_get_cursor(0))
+
+    feed('X')
+    -- Without the fix the hit-enter prompt eats the mapping's "g" keys and the
+    -- cursor stays put.  With the fix "gg" runs and moves the cursor to line 1.
+    t.eq({ mode = 'n', blocking = false }, api.nvim_get_mode())
+    t.eq({ 1, 0 }, api.nvim_win_get_cursor(0))
+  end)
+
   -- oldtest: Test_fileinfo_after_last_bd()
   it('fileinfo is shown after :bd on last listed buffer', function()
     screen = Screen.new(50, 10)

test/old/testdir/test_messages.vim

@@ -758,6 +758,33 @@ func Test_long_formatprg_no_hit_enter()
   call StopVimInTerminal(buf)
 endfunc
 
+" A message shown while a mapping is still being processed must not raise a
+" hit-enter prompt that eats the mapping's remaining keys.
+func Test_hit_enter_no_eat_mapped_keys()
+  CheckRunVimInTerminal
+
+  let lines =<< trim END
+    set ruler
+    call setline(1, range(1, 20))
+    " The 8-line :echo scrolls the screen and would raise a hit-enter prompt;
+    " the mapping then runs "gg" to move the cursor to line 1.
+    nnoremap X :echo "a\nb\nc\nd\ne\nf\ng\nh"<CR>gg
+    normal! 10G
+  END
+  call writefile(lines, 'XtestHitEnterMap', 'D')
+  let buf = RunVimInTerminal('-S XtestHitEnterMap', #{rows: 10})
+  call WaitForAssert({-> assert_match('10,1', term_getline(buf, 10))})
+
+  call term_sendkeys(buf, "X")
+  " Without the fix the hit-enter prompt eats the mapping's "g" keys and the
+  " cursor stays put.  With the fix "gg" runs and moves the cursor to line 1.
+  call WaitForAssert({-> assert_match('1,1', term_getline(buf, 10))})
+  call assert_notmatch('Press ENTER', term_getline(buf, 10))
+
+  " clean up
+  call StopVimInTerminal(buf)
+endfunc
+
 " Test that fileinfo is shown after deleting the last listed buffer with :bd
 func Test_fileinfo_after_last_bd()
   CheckRunVimInTerminal